Question about NoAccel vs Trbvh

Gaming and Visualization Technologies Visualization OptiX
1

Hi:
I recently met an issue when playing with acceleration structures.Hope someone could give me a hand.
In my scene structure it’s just one top_group(Trbvh)->some xfroms-> GeometryGroup(Trbvh)->Geometry Instance->geometry
It works fine.
Now i assign a invisible material to one geometry instance(a material with anyhit just rtIgnoreIntersection())
it still works fine and that object is invisible.

Here comes the issue.
When I apply a scale to the object’s xform and scale it down to 0.99 on x,y,z. That object change to black color instead of invisible.
But if i change the top_group structure to NoAccel. The scaled down object looks invisible again which is what I want.
So far I only found scale down will affect the invisible object. Scale up seems ok. rotation and translation is ok.

my question:
1:is this a bug for trbvh structure? (i also tried Bvh the same issue.)
2:Since NoAccel works fine but it affect performance what’s the better options here?
thanks you

2

That’s potentially a known issue inside OptiX.
Similar case here: [url]https://devtalk.nvidia.com/default/topic/1042855/optix/strange-intersection-issue/[/url]

You could try if the OptiX 5.1.0 experimental execution strategy solves it, but that is really very limited in its implemented features in that version.
[url]http://raytracing-docs.nvidia.com/optix/api/html/group___context_free_functions.html#ga275d371107f1ecae303579c6f61e031a[/url]

3

thanks Detlef for answering my question.
When I try your experimental strategy before the context creation the app crashs.
this is the code i enable:

int expexeconoff = 1;
if (rtGlobalSetAttribute(RT_GLOBAL_ATTRIBUTE_EXPERIMENTAL_EXECUTION_STRATEGY, sizeof(expexeconoff), &expexeconoff) != RT_SUCCESS) {
			printf("Error\n");
}

i’m using optix 5.1 on a titanV with latest driver windows 10.
Will the next release fix this issue?
thanks
Yang

4

If it’s the same error as I think, then it’s not happening in a newer internal version of that code path in OptiX anymore and the next major release should pick it up. I cannot comment on release dates though.